Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 15910)
+++ wp-includes/taxonomy.php	(working copy)
@@ -534,7 +534,7 @@
 		case 'slug':
 		case 'name':
 			foreach ( $terms as $i => $term ) {
-				$terms[$i] = sanitize_term_field('slug', $term, 0, $taxonomy, 'db');
+				$terms[$i] = sanitize_title_for_query($term);
 			}
 			$terms = array_filter($terms);
 
Index: wp-includes/query.php
===================================================================
--- wp-includes/query.php	(revision 15910)
+++ wp-includes/query.php	(working copy)
@@ -1786,7 +1786,7 @@
 		}
 
 		if ( '' != $q['name'] ) {
-			$q['name'] = sanitize_title($q['name']);
+			$q['name'] = sanitize_title_for_query($q['name']);
 			$where .= " AND $wpdb->posts.post_name = '" . $q['name'] . "'";
 		} elseif ( '' != $q['pagename'] ) {
 			if ( isset($this->queried_object_id) ) {
@@ -1814,9 +1814,8 @@
 
 			$page_for_posts = get_option('page_for_posts');
 			if  ( ('page' != get_option('show_on_front') ) || empty($page_for_posts) || ( $reqpage != $page_for_posts ) ) {
-				$q['pagename'] = str_replace('%2F', '/', urlencode(urldecode($q['pagename'])));
 				$page_paths = '/' . trim($q['pagename'], '/');
-				$q['pagename'] = sanitize_title(basename($page_paths));
+				$q['pagename'] = sanitize_title_for_query(basename($page_paths));
 				$q['name'] = $q['pagename'];
 				$where .= " AND ($wpdb->posts.ID = '$reqpage')";
 				$reqpage_obj = get_page($reqpage);
@@ -1828,9 +1827,8 @@
 				}
 			}
 		} elseif ( '' != $q['attachment'] ) {
-			$q['attachment'] = str_replace('%2F', '/', urlencode(urldecode($q['attachment'])));
 			$attach_paths = '/' . trim($q['attachment'], '/');
-			$q['attachment'] = sanitize_title(basename($attach_paths));
+			$q['attachment'] = sanitize_title_for_query(basename($attach_paths));
 			$q['name'] = $q['attachment'];
 			$where .= " AND $wpdb->posts.post_name = '" . $q['attachment'] . "'";
 		}
@@ -1963,7 +1961,7 @@
 					$q['author_name'] = $q['author_name'][count($q['author_name'])-2]; // there was a trailling slash
 				}
 			}
-			$q['author_name'] = sanitize_title($q['author_name']);
+			$q['author_name'] = sanitize_title_for_query($q['author_name']);
 			$q['author'] = get_user_by('slug', $q['author_name']);
 			if ( $q['author'] )
 				$q['author'] = $q['author']->ID;
Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 15910)
+++ wp-includes/formatting.php	(working copy)
@@ -628,6 +628,7 @@
 		chr(197).chr(186) => 'z', chr(197).chr(187) => 'Z',
 		chr(197).chr(188) => 'z', chr(197).chr(189) => 'Z',
 		chr(197).chr(190) => 'z', chr(197).chr(191) => 's',
+		chr(200).chr(153) => 's', chr(200).chr(155) => 't',
 		// Euro Sign
 		chr(226).chr(130).chr(172) => 'E',
 		// GBP (Pound) Sign
@@ -783,19 +784,27 @@
  *
  * @param string $title The string to be sanitized.
  * @param string $fallback_title Optional. A title to use if $title is empty.
+ * @param string $context Optional. The operation for which the string is sanitized
  * @return string The sanitized string.
  */
-function sanitize_title($title, $fallback_title = '') {
+function sanitize_title($title, $fallback_title = '', $context = 'save') {
 	$raw_title = $title;
-	$title = strip_tags($title);
-	$title = apply_filters('sanitize_title', $title, $raw_title);
 
+	if ( 'save' == $context )
+		$title = remove_accents($title);
+
+	$title = apply_filters('sanitize_title', $title, $raw_title, $context);
+
 	if ( '' === $title || false === $title )
 		$title = $fallback_title;
 
 	return $title;
 }
 
+function sanitize_title_for_query($title) {
+	return sanitize_title($title, '', 'query');
+}
+
 /**
  * Sanitizes title, replacing whitespace with dashes.
  *
@@ -816,7 +825,6 @@
 	// Restore octets.
 	$title = preg_replace('|---([a-fA-F0-9][a-fA-F0-9])---|', '%$1', $title);
 
-	$title = remove_accents($title);
 	if (seems_utf8($title)) {
 		if (function_exists('mb_strtolower')) {
 			$title = mb_strtolower($title, 'UTF-8');